Field of the Invention
The present invention relates to an image forming apparatus, for example, a copying machine, a printer, or a facsimile machine, which uses an electrophotographic system or an electrostatic recording system.
Description of the Related Art
Hitherto, for example, as an image forming apparatus using an electrophotographic system, there has been known an image forming apparatus using an intermediate transfer system. In the intermediate transfer system, toner images formed on photosensitive members serving as image bearing members are primarily transferred onto an intermediate transfer member and thereafter secondarily transferred onto a transfer material such as paper.
In Japanese Patent Application Laid-Open No. H09-50167, the following method is disclosed. A residual toner, which remains on the intermediate transfer member without being transferred onto a transfer material, is charged to a polarity opposite to an original charging polarity of the toner, and thereafter is moved from the intermediate transfer member to the photosensitive member simultaneously with the primary transfer. The residual toner which is moved to the photosensitive member is collected by a photosensitive member cleaning unit configured to clean the photosensitive member.
In Japanese Patent Application Laid-Open No. H09-50167, the residual toner on the intermediate transfer member is charged to the polarity opposite to the original charging polarity of the toner. As a result, there is a case where an electrostatic attractive force between the residual toner and the photosensitive member acts more strongly than an electrostatic attractive force between the toner charged to the original charging polarity and the photosensitive member. Typically, that is a case where the photosensitive member is charged to the same polarity as the original charging polarity of the toner. Therefore, there is a case where cleaning performance for the photosensitive member is degraded.
As a countermeasure for such a problem, it is conceivable to make improvement in cleaning performance of the photosensitive member cleaning unit. However, improvement in cleaning performance may shorten a lifetime of the photosensitive member and the like. For example, as the photosensitive member cleaning unit, there has often been used a cleaning blade (rubber blade) being a cleaning member arranged in abutment against the photosensitive member. In order to improve the cleaning performance of the cleaning blade, it is conceivable to increase an intrusion amount or a contact pressure of the cleaning blade with respect to the photosensitive member. However, in such a case, rubbing of the photosensitive member and the cleaning blade may increase the amount of abrasion of the photosensitive member and the cleaning blade. As a result, the lifetime of the photosensitive member and the cleaning blade may be shortened.
As described above, in consideration of the cleaning performance for the photosensitive member and the lifetime of the photosensitive member and the cleaning blade, it is desired that the amount of toner, which is to be charged to the polarity opposite to the original charging polarity and is to be moved from the intermediate transfer member to the photosensitive member, be as small as possible.